Construction of compressor rotors



March 13, 1956 R, G. A. EDWARDS 2,738,126

CONSTRUCTION OF COMPRESSOR ROTORS Filed Nov. 15 1951 2 Sheets-Sheet 1l/lIl/EIY TOR R. a. A. EDWARDS March 13, 1956 R. G. A. EDWARDSCONSTRUCTION OF COMPRESSOR ROTORS 2 Sheets-Sheet 2 Filed Nov. 15, 1951M/V A/ 7 0/? 1 G. 14. EDVVWDS 37M $21M United States Patentf) ce 72,738,126 CONSTRUCTlDN OF CGIVIPRESSOR ROTORS Reginald G..A. Edwards,Coventry, England, assignor to Armstrong Siddeley Motors Limited,Coventry, England Application November 15, 1951, Serial No. 256,475

Claims priority, application Great Britain December 8, 1950 2 Claims.(Cl. 230134) 7 to which it will be subjected when rotating at highspeeds.

According to the invention, a bladed compressorrotor comprises aplurality of discs most of which have an axially-extending peripheralportion which forms a shroud between two adjacent blade rows of therotor and the axial extremity of which has a spigotal engagement withthe next disc, the two discs jointly providing a radial-locatingperipheral groove, for the roots of a blade row, when bolted together,radially inwardly of a the roots of' that row, through theirspigotally-engaging portions.

The term bolt is used herein in a generic sense to include the use ofscrews, nuts and bolts, nuts and studs or the like.

In practice all the discs may beas aforesaid, except for the end ones.Preferably the two end discs are of steel and fast with shaft portionsjournalled in a diaphragm or other portion of the stator, and all theother discs, which may be of aluminium or other light alloy, areperipherally supported from the end ones. In particular, the said otherdiscs may be relatively-thin, plain discs with slightly enlarged hollowhubs providing a passage for cooling air. Near its periphery each of thelight alloy discs is provided, at one side, with a short axial flangewithin which spigots the axial extremity of the aforesaidaxially-extending portion of the adjacent disc, and radially outwardlyof this flange is the radiallocating peripheral groove for the roots ofa blade row. As will be well understood, such groove may be ofT-section, fir-tree section, or preferably of dovetail section. Thespigotal engagement between each light alloy disc and the axialextremity of the axially-extending peripheral portion of an adjacentdisc ensures concentricity.

The steel disc at one end may have a spigotal engagement with anindependent, axially-extending n'ng (preferably of light alloy)providing the adjacent shroud and bolted to the steel disc jointly toprovide therewith the radial-locating peripheral groove for the roots ofthe blade row at that end.

All the blades may be inexpensively formed of a plastic moulded to shapeand incorporating a filler of asbestos or other heat-resisting material.

Preferably the light-alloy discs are die cast, to obviate the necessityfor machining; but when the discsare not die cast the machiningoperations are easy turning ones, which allows of their production atlow cost.

Preferably the axes of each set of retaining bolts lie on a pitch circlewhich is coincident with the cylindrical surface of the, spigotalengagement, being as near the blade roots as is conveniently possible.

In the drawings:

Figure 1 is a diagrammatic view of a gas turbine engine 2,738,126Patented Mar. 13, 1956 including an air intake A, an axial-flowcompressor B,

an annular combustion chamber C (although this latter could be a ring ofseparate combustion chamber units), an axial-flow turbine D, and a jetpipe E;

Figure 2 is an axial section of an axial-flow compressor constructed inaccordance with the invention, parts being omitted for the sake ofclearness;

Figure 3 is a fragmentary section similar to Figure 2 but to a largerscale and showing rotor blade roots of a different form;

Figure 4 is a view similar to Figure 3 but showing a modifiedconstruction;

Figures Sand 6 are sections, respectively, on the lines 5-5 and 6-6 ofFigure 4;

Figure 7 shows a modified (as compared with Figure 5) form of blade formounting in the compressor; and

Figure 8 is an exploded, fragmentary perspective view showing therelationship between one of the fixing bolts and one of the spigotingparts.

In Figures 2 and 3 the compressor, of which an intermediate length hasbeen omitted, has rows of radial stator blades 11, 11 fast at theirradially-outer ends with a stator casing 12, and, at the upstream anddownstream ends, respectively, the stator has diaphragms 13, 14 whichsupport bearing 15, 16 for aligned shaft portions 17, 18

, fast with the opposite ends of the rotor.

The latter comprises steel end discs 19, Zli, of which central hubsprovide the shaft portions 17 and 18, and

intermediate discs 21, 21 (two only of which are shown). Each of thediscs 21, which are of light alloy, is formed with an axially-extendingperipheral portion 22 having a flange 23 spigotally engaged within anoppositely, axiallydirected annular flange 24 of the discadjacent itsrighthand side in Figure 2, the portion 22 of the extreme right-handdisc 21 (not shown) having a similar engagement with a similar flange24a of the right-hand end disc 20. An independent axially-extending ring22a has flanges 23a and 23b similarly spigotally engaging within theflange 24 of the left-hand disc 21, and a flange 24b of the left-handend disc 19, respectively.

\ These spigotal engagements can best be seen at the bottom of Figure 2,while at the top of the latter, and in Figures 3 and 8, can best be seenthe way the discs are bolted together. The bolts 25 (some only of whichare shown) are inserted in bores which have their axes aligned with theaxially-directed surfaces of the spigotally engaging flanges, and thebolts have shoulders 26 intermediate-their ends (although the bolts 25asecuring the ring 22ato the end disc 19 may be unshouldered).

These shoulders seat on steps 27 at the bottom of counterbores in theportions 22 (or ring 22a, as appropriate) for their outer radialsurfaces to lie flush with the radial surfaces 28'at the roots of theflanges 23, 23a, and they are located by lock-nuts 29. This anchors thebolts, and the disc at the right-hand side, during assembly, can he slidonto the extending ends of the bolts and be secured by nuts 30.

Each disc 21 has a central hole 50, for cooling air.

Radially-outwardly of the spigotally-engaging flanges the discs 19, 20and 21, and the portions 22 and ring 22a have grooves 31 to receive theroots 32 of associated rows of rotor blades 33, and the portions 22 andring 22a act as shrouds between the rows. It can be arranged, accordingto the profile of the rotor blade roots, for there to be axial clearancebetween the bottoms of the grooves and the roots (as shown in Figure 2)and for flanges 34 to grip necks of the roots when the nuts 30 aretightened, or for the grooves and roots to have a wedging engagement asshown in Figure 3 or 4.

As shown in Figure 2 the compressor can have air-inlet guide vanes 35,and air-outlet guide vanes 36, these vanes being fast with the statorand the vanes 36 directing the compressed air into passages 37, 38, 39leading to a combustion chamber.

The embodiment shown in Figures 4 to 6 differs from that of Figure 2mainly in the way the blades, which are preferably of molded plastic,are supported. In this case the blades 33 are fast with platforms 40which are chamfered at the up-stream and down-stream edges to have adovetail engagement with the grooves 31a. The intermediate edges 41 ofthe platforms are also chamfered and are located by reversely bevellededges of fillets &2, the up-stream and down-stream edges of the filletsalso being bevelled to have a dovetail engagement with the grooves 31a.As shown in Figure the platforms (and, of course, the fillets) areparallelogram-like in plan.

T he blade shown in Figure 7 has a rectangular platform 40a of which theup-stream and down-stream edges are bevelled, like those of the platform40 of Figure 5, to have a dovetail engagement with the grooves 3111, theintermediate edges 41a in this case lying in planes which are radial ofthe rotor axis so as to pack closely together when the blades of a roware assembled.

For lightening the portions 22 and the ring 2201 their radially inneredges can be relieved, as indicated at 44 in Figure 6, intermediate thebolting positions where bosses 43 are left to accommodate the bolts 25,25a. Also for lightening purposes, the platforms 4i and 40a can behollowed on the underside as shown in Figure 4.

What I claim as my invention and desire to secure by Letters Patent ofthe United States is:

l. A demountable axial-flow bladed compressor rotor comprising oppositeend discs fast with respective outwardly-extending coaxial shaftportions, a plurality of concentric intermediate thin discs withaxially-extending peripheral portions at their corresponding one sides,each of said axially-extending portions having at its extremity aradially-inwardly directed flange which is formed on its outer axialside for spigotal engagement with the adjacent disc, anaxially-extending ring between said end disc and the extremeintermediate disc whose axially-extending portion is remote from theadjacent end disc, said ring being provided at its ends withradially-inwardly directed flanges which are formed on their outer axialsides for spigotal engagement respectively with the adjacent end andintermediate discs, said ring and axially-extending peripheral portionsconstituting shrouds and supporting said intermediate discs from saidend discs in mutually spaced relation whereby to form a light hollowstructure which is internally reinforced against centrifugal loads bysaid discs and which is supported from said shaft portions, each saidaxially-extending portion and each end of said ring also forming withthe disc to which it is spigoted a peripheral groove for locating a rowof rotor blades, said adjacent end disc, the radially-inwardly directedflange of said ring remote from said adjacent end disc, and each saidradially-inwardly directed flange of said axiallyextending portionshaving fast therewith a circle of bolts which extend parallel to theaxis of the compressor through a corresponding circle of coacting holeswhich is in the adjacent spigotally-engaged part and intersected by thecylindrical surface of the spigotal engagement, and detachable nuts onthe extending ends of said bolts whereby said ring, saidaxially-extending portions and said adjacent discs are demountably heldin assembled relation with the associated blade rows detachably clampedin said peripheral grooves.

2. A demountable axial-flow bladed compressor rotor comprising oppositeend discs fast with respective outwardly-extending coaxial shaftportions, a plurality of concentric intermediate thin discs withaxially-extending peripheral portions at their corresponding one sides,each of said axially-extending portions having at its extremity aradially-inwardly directed flange formed on its outer axial side with anannular step, each of said intermediate discs on the side opposite saidaxially-extending portion formed with an annular ridge, the adjacentsteps and ridges forming a spigot for inter-engaging adjacent discs andaxially-extending portions, said axially-extending portions formingshrouds, an axially-extending ring between the extreme intermediate discwhose axiallyextending portion is remote from the adjacent end disc andsaid end disc, said ring having at each end a radiallyinwardly directedflange, said ring flanges each having an annular step, the said end dischaving an annular ridge for spigotal engagement with the adjacentannular step of said ring and the other annular step of said ringspigotally engaging the ridge of the adjacent intermediate disc, saidring forming a shroud, said ring and axiallyextending portionssupporting said intermediate discs from said end discs in mutuallyspaced relation whereby to form a light hollow structure which isinternally reinforced against centrifugal loads by said discs and whichis supported from said shaft portions, each said axiallyextendingportion and each end of said ring also forming with the disc to which itis spigoted a peripheral groove for locating a row of rotor blades, saidadjacent end disc, the radially-inwardly directed flange of said ringremote from said adjacent end disc, and each said radially-inwardlydirected flange of said axially-extending portions having fast therewitha circle of bolts which extend parallel to the axis of the compressorthrough a corresponding circle of coacting holes which is in theadjacent spigotally-engaged part and intersected by the cylindricalsurface of the spigotal engagement, and detachable nuts on the extendingends of said bolts whereby said ring, said axially-extending portionsand said adjacent discs are demountably held in assembled relation withthe associated blade rows detachably clamped in said peripheral grooves.

References Qitetl in the file of this patent UNITED STATES PATENTS768,597 Geisenhoner Aug. 30, 1904 980,732 Anderson Jan. 3, 19111,118,361 Lasche Nov. 24, 1914 FOREIGN PATENTS 394,001. Great BritainJune 19, 1933 578,191 Great Britain June 19, 1946 599,809 Great BritainMar. 22, 1948 642,287 Great Britain Aug. 30, 1950 729,493 Germany Dec.17, 1942

